Abstract
An ultrasonic phased array device is developed to provide mobility aid for visually impaired people. To perform acoustic imaging, two different linear transducer arrays are constructed using commercially available transducers. The transmitter and receiver arrays are formed with six and four transducer elements, respectively. Individual transducer elements are discrete components with a radius of 1.9 wavelengths and a half-power beamwidth of 43deg at 40.8 kHz center frequency. The transmitter array is formed by aligning the transducers with minimum spacing between the elements. Even this placement leads to the occurrence of unwanted grating lobes in the array response and decreases the field-of-view to 30deg . To eliminate these grating lobes, the elements of the receiver array are placed with a different spacing. Forming the receiver and transmitter arrays with nonidentical element spacing makes the grating lobes to appear at different places. Since the response of the overall system is the product of the directivity patterns of receiver and transmitter arrays, the grating lobes diminish for the overall system and the field-of-view increases.
Highlights
A COUSTIC imaging technology is widely used for medical purposes, underwater imaging and nondestructive testing applications [1]
To measure the performance of the developed phased array device, experiments are performed on a set of objects with various shapes placed at different locations
If identical receiver and transmitter arrays with an inter-element spacing of 2λ were used, a grating lobe would appear at −14◦ for a beamsteering angle of 16◦
Summary
A COUSTIC imaging technology is widely used for medical purposes, underwater imaging and nondestructive testing applications [1]. In the past few decades acoustic imaging in air became popular with advances in air coupled transducers [2] This led to the introduction of several electronic travel aid devices to improve the mobility of visually impaired people. A recent device that uses the phased array technique is an ultrasonic obstacle detector introduced by Strakowski, Kosmowski, Kowalik, and Wierzba in 2006 [14]. We present the design and experimental verification of an ultrasonic phased array device for acoustic imaging in air. This placement strategy increases the Field of View (FOV) beyond the halfpower beamwidth of individual transducer elements
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